JPA - esempi di utilizzo

Alcuni esempi di utilizzo di Java Persistence API (JPA)...

- Storing di un oggetto

private void saveButtonActionPerformed(ActionEvent evt) {
Address address = new Address();
address.setCustomerNo( customerNoText.getText() );
address.setLastname( lastnameText.getText() );
address.setFirstname( firstnameText.getText() );
address.setStreet( streetText.getText() );
address.setPostcode( postcodeText.getText() );
address.setCity( cityText.getText() );

EntityManagerFactory emf = Persistence.createEntityManagerFactory(
 "JPATutorialPU" );
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();

try {
 em.persist( address );
 em.getTransaction().commit();
} catch (Exception e) {
 System.out.println( e.getMessage() );
 em.getTransaction().rollback();
} finally {
 em.close();
}
}

- Lettura di un oggetto

private void loadButtonActionPerformed(java.awt.event.ActionEvent evt) {                                        

EntityManagerFactory emf = Persistence.createEntityManagerFactory(
 "JPATutorialPU" );
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();

String customerNo = JOptionPane.showInputDialog(
 null,
 "Enter customer number",
 "Input",
 JOptionPane.QUESTION_MESSAGE);

try {
 Query query = em.createQuery(
   "SELECT a FROM Address a WHERE a.customerNo = :customerNo");
 query.setParameter(
   "customerNo",
   customerNo);

 Address address = (Address) query.getSingleResult();

 customerNoText.setText( address.getCustomerNo() );
 lastnameText.setText( address.getLastname() );
 firstnameText.setText( address.getFirstname() );
 streetText.setText( address.getStreet() );
 postcodeText.setText( address.getPostcode() );
 cityText.setText( address.getCity() );

} catch (Exception e) {
 System.out.println( e.getMessage() );
 em.getTransaction().rollback();
} finally {
 em.close();
}
}